A model is proposed that quantitatively describes the 1-octanol/water distribution coefficients of methylmercuric species in terms of the 1-octanol/water partition coefficients of each individual methylmercuric species (i.e., CH3HgCl0, CH3HgOH0, and CH3Hg+) and the aqueous-phase equilibrium speciation of the methylmercuric species CH3HgCl0, CH3HgOH0, and CH3Hg+.